Software Framework for Evolving Specifications in Process Control System

1. A method of implementing an application in a process control system containing a plurality of field devices operable to implement desired control processes, each of said plurality of field devices having a corresponding one of a plurality of device descriptions indicating capabilities of the field device, said plurality of device descriptions being provided according to a set of specifications, said method comprising: providing a plurality of version objects, wherein each of said plurality of version objects respectively corresponds to a corresponding one of an ordered sequence of versions of a first specification and is designed to be instantiated by a corresponding one of a plurality of class factories, wherein each of said plurality of version objects is designed to process changes in a corresponding version compared to a prior version of said ordered sequence, said first specification being contained in said set of specifications; forming a factory information representing the specific one of class factories which can be used to instantiate the corresponding version object; receiving a version identifier and an input data that is to be processed for managing a first field device of said plurality of field devices, said version identifier corresponding to a first version in said ordered sequence of versions and said first field device having a first device description provided according to said first version of said first specification, wherein said input data represents a portion of said first device description, said first device description being contained in said plurality of device descriptions; examining said factory information to select a first class factory corresponding to said first version, said first class factory being designed to instantiate a first version object which in turn is designed to process said input data; instantiating a version instance of said first version object using said first class factory selected based on said examining; and processing said input data using said version instance to identify device capability of said first field device, as a basis for management of said first field device.

2. The method of claim 1 , wherein said factory information is in the form of a linked list of a plurality of nodes, wherein each node points to a corresponding class factory, wherein said examining determines said first class factory by traversing said linked list.

3. The method of claim 2 , wherein said determining determines said first class factory as corresponding to a version object of a version number greater than or equal to said version identifier.

4. The method of claim 3 , wherein each of said plurality of class factories derives from a same base factory, which also defines a create instance method to instantiate said version instance.

5. The method of claim 4 , wherein each of said plurality of version objects except a version object for the start version derives from a version object designed to process an immediate previous version.

6. The method of claim 5 , wherein said plurality of version objects contains a last version object designed to handle sections defined by any higher version for which version objects are not provided, wherein each section represents a portion of said input data.

7. The method of claim 6 , wherein said last version object tolerates processing sections added or modified by said any higher version.

8. The method of claim 6 , wherein said application is upgraded to support a new version, further comprising: adding a new version object which derives from an object designed to process sections changed or added by a previously highest version of a standard supported by said application; adding a new class factory which is designed to instantiate said new version object; inserting a new node into said linked list corresponding to said new class factory, wherein said new node is placed between a pair of nodes corresponding to said previously highest version and said last version object.

9. The method of claim 6 , wherein each of said plurality of version objects except said version object of said start version is designed to invoke a method from a base version from which the version object derives to process each section, wherein each of said plurality of version objects returns a failure indication when the section cannot be processed by the version object, wherein each of said plurality of version objects returns a success indication when the section can be successfully processed, wherein each of said plurality of version objects passes a success indication to the invoking version object when a success indication is received, and wherein each of said plurality of version objects uses a handling logic to process the section if the corresponding process section method exists and a failure indication is received.

10. The method of claim 9 , wherein said application comprises a parser, said input data comprises device descriptions used in the management of a plurality of field devices in said process control plant.

11. A machine readable medium storing one or more sequences of instructions for causing a system to parse device descriptions in the management of a plurality of field devices in a process control plant, said plurality of field devices operable to implement desired control processes, each of said plurality of field devices having a corresponding one of a plurality of device descriptions indicating capabilities of the field device, said plurality of device descriptions being provided according to a set of specifications, wherein each device description is in one of an ordered sequence of versions of a first specification and contains a plurality of sections, wherein execution of said one or more sequences of instructions by one or more processors contained in said system causes said system to perform the actions of: providing a plurality of parser objects, wherein each of said plurality of parser objects respectively corresponds to one of a corresponding said ordered sequence of versions and is designed to be instantiated by a corresponding one of a plurality of class factories, wherein each of said plurality of parser objects is designed to parse at least a set of sections added or modified by a corresponding version compared to a prior version of said ordered sequence, said first specification being contained in said set of specifications; forming a factory information representing the specific one of class factories which can be used to instantiate the corresponding parser object; receiving a version identifier of a device description that is to be parsed for managing a first field device of said plurality of field devices, said version identifier corresponding to a first version in said ordered sequence of versions and said device description provided according to said first version of said first specification, said device description being contained in said plurality of device descriptions; examining said factory information to select a first class factory corresponding to said first version, said first class factory being designed to instantiate a first parser object which in turn is designed to parse said device description; instantiating a parser instance of said first parser object using said first class factory selected based on said examining; and processing said device description using said parser instance to identify device capability of said first field device, as a basis for management of said first field device.

12. The machine readable medium of claim 11 , wherein said factory information is in the form of a linked list of a plurality of nodes, wherein each node points to a corresponding class factory, wherein said examining determines said first class factory by traversing said linked list.

13. The machine readable medium of claim 12 , wherein said determining determines said first class factory as corresponding to a parser object of a version number greater than or equal to said version identifier.

14. The machine readable medium of claim 13 , wherein each of said plurality of class factories derives from a same base factory, which also defines a create instance method to instantiate said parser instance.

15. The machine readable medium of claim 14 , wherein each of said plurality of parser objects except a parser object for the start version derives from a parser object designed to parse an immediate previous version.

16. The machine readable medium of claim 15 , wherein said plurality of parser objects contains a last parser object designed to handle sections defined by any higher version for which parser objects are not provided, wherein said last version object tolerates processing sections added or modified by said any higher version.

17. The machine readable medium of claim 16 , wherein said last parser object returns an error code when parsing sections added or modified by said any higher version, thereby providing tolerance to changes in said any higher version.

18. The machine readable medium of claim 16 , wherein said parser is upgraded to support a new version of said standard, further comprising: adding a new parser object which derives from an object designed to parse sections changed or added by a previously highest version of said standard supported by said parser; adding a new class factory which is designed to instantiate said new parser object; inserting a new node into said linked list corresponding to said new class factory, wherein said new node is placed between a pair of nodes corresponding to said previously highest version and said last parser object.

19. The machine readable medium of claim 18 , wherein each of said plurality of parser objects except said parser object of said start version is designed to invoke a method from a base version from which the parser object derives to parse each section, wherein each of said plurality of parser objects return a failure indication when the section cannot be parsed by the parser object, wherein each of said plurality of parser objects returns a success indication when the section can be successfully parsed, wherein each of said plurality of parser objects passes a success indication to invoking parser object when a success indication is received, and wherein each of said plurality of parser objects uses a handling logic to parse the section if the corresponding process section method exists and a failure indication is received.

20. A digital processing system operating in a process control plant containing a plurality of field devices operable to implement desired control processes, each of said plurality of field devices having a corresponding one of a plurality of device descriptions indicating capabilities of the field device, said plurality of device descriptions being provided according to a set of specifications, said digital processing system comprising: a secondary storage to provide a plurality of version objects and a plurality of class factories, wherein each of said plurality of version objects respectively corresponds to a corresponding one of an ordered sequence of versions of a first specification and is designed to be instantiated by a corresponding one of said plurality of class factories, wherein each of said plurality of version objects is designed to process changes in a corresponding version compared to a prior version of said ordered sequence, said first specification being contained in said set of specifications; a processor to form a factory information representing the specific one of class factories which can be used to instantiate the corresponding version object; an interface to receive a version identifier and an input data that is to be processed for managing a first field device of said plurality of field devices, said version identifier corresponding to a first version in said ordered sequence of versions and said first field device having a first device description provided according to said first version of said first specification, wherein said input data represents a portion of said first device description, said first device description being contained in said plurality of device descriptions, wherein said processor is operable to: examine said factory information to select a first class factory corresponding to said first version, said first class factory being designed to instantiate a first version object which in turn is designed to process said input data; instantiate a version instance of said first version object using said first class factory selected based on said examining; and process said input data using said version instance to identify device capability of said first field device, as a basis for management of said first field device.

21. The digital processing system of claim 20 , wherein said plurality of version objects contains a last version object designed to handle sections defined by any higher version for which version objects are not provided, wherein each section represents a portion of said input data.